1. Field of the Invention
The present invention relates to optical equipment having a lens position detector.
2. Related Background Art
In a prior art lens position detector in a video camera, a light from a light emitting diode is irradiated to a detection pattern formed on a lens barrel (for example, a Gray code pattern formed on a substrate) and a reflected light is detected by a photo-transistor to read the detection pattern to produce position information, or a so-called noncontact frequency generator is used. For example, a rotation speed of a motor is optically detected by providing a pulse disk on the motor in accordance with the principle described above.
However, in the prior art Gray code system, it is necessary to increase the number of bits of the Gray code when high precision and resolution are required in the lens position detection. As a result, the size of the detector increases. Further, there is a limit in reducing the pattern size of the Gray code. The frequency generator system is effective to a DC motor having a reduction gear mechanism (which is used at a high rotation speed) but it is not suitable to a direct lens drive system without a reduction gear mechanism.